1. Field of the Invention
The present invention relates generally to a communication system using multiple carriers (a “multicarrier communication system”), and in particular, to a data transmission/reception system and method for applying differential signal combination schemes according to priority of data, for segment management.
2. Description of the Related Art
The 4th generation (4G) communication system, which is the next generation communication system, aims at providing users with services having various Quality-of-Services (QoSs) at a data rate of about 100 Mbps.
To this end, in the 4G communication system, active research is being conducted on an Orthogonal Frequency Division Multiplexing (OFDM) scheme which is useful for high-speed data transmission over wire/wireless channels. The OFDM scheme, one of the schemes for transmitting data using multiple carriers, is a type of a Multi-Carrier Modulation (MCM) scheme that converts a serial input symbol stream into parallel symbols and modulates each of the symbols with a plurality of orthogonal sub-carriers, i.e., sub-carrier channels, before transmission.
Although the OFDM scheme is similar to the conventional Frequency Division Multiplexing (FDM) scheme, it is characterized by the following: obtaining optimal transmission efficiency during high-speed data transmission, maintaining orthogonality between multiple sub-carriers during transmission, and obtaining optimal transmission efficiency during high-speed data transmission due to its high frequency efficiency and its robustness against multipath fading. In addition, the OFDM scheme is regularly used for communication system architecture because it is robust against frequency selective fading, multipath fading and impulse noise, and can reduce Inter-Symbol Interference (ISI) using a guard interval and can design an equalizer in a simple hardware structure.
Generally, the OFDM scheme has high spectrum efficiency because spectrums between sub-carrier channels overlap each other, maintaining orthogonality there between. The OFDM scheme implements modulation by Inverse Fast Fourier Transform (IFFT), and demodulation by Fast Fourier Transform (FFT). A multiple access scheme based on the OFDM scheme includes an Orthogonal Frequency Division Multiple Access (OFDMA) scheme that allocates some of all sub-carriers to a particular mobile subscriber (MS). The OFDMA scheme does not need spreading sequences for spreading, and can dynamically change a set of sub-carriers allocated to a particular MS according to a fading characteristic of the wireless transmission path.
Therefore, development of the 4G communication system takes into account both the software aspect for developing various contents and the hardware aspect for developing a high-spectrum efficiency wireless access scheme to provide the highest QoS. Below is a general description of the hardware aspect taken into account in the 4G communication system.
In wireless communications, the high-speed, high-quality data service is generally affected by the channel environment. In the wireless communications, the channel environment is subject to frequent changes due to the Additive White Gaussian Noise (AWGN), as well as to power variation of received signals, caused by fading, shadowing, a Doppler effect caused by movement of an MS and a frequent change in moving velocity, and interference by the other MSs and multipath signals. Therefore, in order to provide high-speed wireless packet data service, there is a need for new advanced technology capable of adaptively coping with the channel variation in addition to the schemes provided in the conventional 2nd generation (2G) or 3rd generation (3G) communication system. Such schemes as an Adaptive Modulation and Coding (AMC) scheme and a Hybrid Automatic Retransmission Request (HARQ), used in the existing communication systems, also adaptively cope with the channel variation, contributing to dramatic improvement in the total system performance.
Notwithstanding the use of the AMC scheme and the HARQ scheme cannot solve the basic problem of lack of radio resources in wireless communications. Therefore, in order to maximize the subscriber capacity and enable the high-speed data transmission essential for multimedia service, there is a need for continued research of high-spectrum efficiency multiple access schemes.
With regards to high-speed, high-quality packet data service, there is a lively discussion on new multiple access schemes that have high spectrum efficiency and can guarantee priority of data. One of the new multiple access schemes is to differentiate transmission strategies in the communication systems, for data transmission, and as one of such communication systems, a Differential Segment System is now under discussion.
The Differential Segment System classifies types of segments and differentiates its transmission strategy according to a channel state and a type of data, for data transmission. The Differential Segment System classifies various segments and transmits data according to each segment type. Currently, there is no specific scheme proposed for setting segment types. Thus, there is a demand for a specific segment management scheme in a communication system that manages segments by applying a technology for coping with the channel variation using the segment type.